1. Field of the Invention
The present invention relates to a lens barrel that is provided in an image pickup apparatus such as a film camera or a digital camera, and an image pickup apparatus having the lens barrel.
2. Description of the Related Art
In conventional lens barrels of this type, with increases in zooming magnification, the number and strokes of optical members such as lens groups have increased, and the layout of cam grooves arranged in an inner peripheral surface of a cam cylinder according to movement of each optical member along an optical axis has become more complicated.
Also, to enable a plurality of optical members straight ahead while inhibiting them from rotating, straight-ahead movement guide grooves that guide respective base portions of cam followers arranged in the plurality of optical members are formed in a straight-ahead moving cylinder. Thus, due to an increase in the number of straight-ahead movement guide grooves, machining of the straight-ahead moving cylinder becomes more complicated, and also, the strength of the straight-ahead moving cylinder deteriorates, causing engagement of the base portions of the cam followers and the straight-ahead movement guide grooves to become unstable.
Accordingly, there has conventionally been proposed a technique that base portions of cam followers in a plurality of optical members are caused to follow a single straight-ahead movement guide groove along an optical axis so that the plurality of optical members can move straight ahead while being inhibited from rotating (Japanese Laid-Open Patent Publication (Kokai) No. H10-39188).
However, according to the technique disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H10-39188, the base portions of the cam followers in the plurality of optical members which follow the single straight-ahead movement guide groove along the optical axis have to be identical in shape, and also, the cam followers in the plurality of optical members have to be identical in circumferential phase.
For this reason, the cam followers in the plurality of optical members overlap in the direction of the optical axis, and the length of a lens barrel in the direction of the optical axis increases accordingly, which hinders miniaturization of an image pickup apparatus.